1. Field of the Invention
This invention generally relates to a linear motion guide assembly and in particular to a small-sized rolling contact type linear motion guide assembly using a plurality of rolling members. More specifically, the present invention relates to an endless linear motion guide assembly.
2. Description of the Prior Art
A linear motion guide assembly is well known in the art and it generally includes a rail extending over a length, a slider mounted on the rail for movement along the rail and a plurality of rolling members for providing a rolling contact between the rail and the slider. In such a linear motion guide assembly, a guide rail is provided with a pair of inner guide grooves on opposite sides and a slider is provided with a pair of outer guide grooves each of which is located opposite to the corresponding one of the pair of inner guide grooves of the rail. And, a plurality of rolling members, typically balls, are interposed between the rail and the slider to provide a sliding contact between them. In an endless linear motion rolling contact guide assembly, a slider is typically provided with a pair of endless circulation path which includes a load path section, a return path section and a pair of curved connecting sections, each connecting the corresponding ends of the load and return path sections. In this case, the load path section is defined by the outer guide groove of the slider and a corresponding portion of the inner guide groove of the rail. The rolling members are provided in the endless circulation path so that the rolling members roll along the endless circulation path as the slider moves along the rail, whereby those rolling members located in the load path section provide a rolling contact between the slider and the rail.
In such a linear motion guide assembly, the balls are maintained in position only when the assembly is maintained in an assembled state. For example, when the slider is separated from the rail, the rolling members will fall off. In order to prevent this from occurring, a stopper is provided at each end of the rail to prevent the slider from slipping away from the rail. However, such a linear motion guide assembly is rather difficult to assemble because the rolling members tend to fall off. Under the circumstances, there has been proposed to provide a retainer plate in the slider to prevent the rolling members from falling off through an opening defined at the load path section when disassembled. However, the provision of such a retainer plate is not always advantageous because it tends to increase the sliding resistance of the rolling members and create a hindrance to make the entire structure smaller. Moreover, difficulty is normally encountered in fabricating and assembling such a linear motion guide assembly having a retainer plate.